Electronic time delay circuit



May 2, 1950 F. J. BIAS ET AL 2,506,335

ELECTRONIC TIME DELAY CIRCUIT Original Filed Nov. 17, 1944 SOURCE OF OBSERVED OSCILLATIONS SOURCE OF SINE Inventors: Fnank J. Bias, Hanold W Lord,

Their Attorney.

WAVE

VOLTAGE Patented May 2, 1950 ELECTRONIC TIME DEEAY CIRCUIT Frank J. Bias; Scotia, and Harld- W..Il0rd.. Sche,-.

nectady, N.. Y., assignors to General Electric. Company, a corporation of New York Original application November'l'l. 1944,2Srial No; 563,920. Divided and this a-pplication April 1-9; 1946, SerialNo. 663,320

2' Claims. 1

Our.. inventionmelates to electric timing cir'-. cuits, andis particularly applicable to use in conjunction with cathode ray apparatus of the type used, for analyzing electric oscillations.

Thisapplication is adivision of our copending application Serial No. 563,920, filed November 17,. 15.44,, now United States Patent 2,449,801,. issued, September 2 1948, and assigned to. the same assignee as the instant application.

It is a general object of thisinventr'on to provide. a new and. improved electric timing circuit.

It islafurther object of this invention to provide anew and improvedelectric time. delay circuit particularly suitable forintroducing a predetermined, phase shift between a series of re.- currenti'nput voltage pulses and. a series. of recurrent. output voltage pulsesin electric translating apparatus.-

Our invention itself, together with further ob- J'ccts. and advantages thereof, will be more fully understocdlby referring now to thenfollowing dc.- tailed specificat on taken in conjunction with the accompanying drawing. the single figure of which is. a schematiccircuit diagramv of a oaths .oda. ray oscillograph apparatus embodying. our invention.

Referringnow to the drawingwe have shown our invention applied to a cathode ray oscillograph apparatus, comprising: a cathode ray discharge device I, asource 2 of electric oscillations to be, observed, and a source 3 of substantially constant frequency oscillations. controlling the sweep and intensity of the electron beam and synchronizing the operation of the source zwith the beam sweep.

The, source of sine wavevoltage 3 may be an oscillator of any WeILKnovJntype, such as a crystal" or resonant circuit oscillator, and preferably includes suitable means, such as a variablecondenser, inductance, or the like controlled by a dial 4 for varying the frequency of the generated oscillations. The sine wave oscillations of selectable constant frequency from the source 3 are amplified and distorted by an amplifier 5 and supplied to a differentiating circuit comprising aicapacitor 6 and a resistor 1 connected across the output of .the amplifier 5.

A; transformer 8. havingits primary winding 9; connected across the resistor 1. supplies from its secondary winding I B. a series of recurrent voltage pulses to theinputof anamplifying electron. discharge device. H having an anode Ila device includes a source oinegative bias P mission. line. section 29..

circuit relation with the transformer winding.

l0. and a grid. bias. resistor. It. The highefrequency oscillations from the transformer wi'ndl-I' ing. Is are supplied. to thev control electrode, of the dscharge. device ll through a capacitor I24 connected in. parallel circuit relation with the resistor 53. It will be understood that, because of differentiation of thedistorted; amplifier. output wave in thecircuit 8, 1, the output of the transformer 8 comprises an alternate series of positive andnegative pulses, The negative voltage pulses supplied to the control electrodeof the. discharge device ll have noelfect, since the control electrode is normally biasednegative and any negative. voltage pulse serves only to. drive the. discharge device I! farther into the cut-,ofl' region. The positivepulses from the transformer winding If], however overcomethe negative bias from the, source L2 thereby to render thev dis,- charge device Ll recurrentl-y conductive for short intervals at a frequency determined by the frequency. of the source. 3...

The. 1).SllllV8' voltage. pulses suppliedto the in put of the discharge device H are amplified and supplied as: negative pulses from the anode of the device. LI tothe anodeof aregenerativepulse generating electron discharge device. I 5 having an anode 5, a cathode I? and a-control electrode law In response to the triggering impulses supplied to the discharge device 5.5 from the discharge device H a pulse generating circuit associated with the device. lcgprcduces a series of re;- currentvoltage pulses having a. frequencye'qual tov the frequency of the triggering pulses. The pulse generating, circuit associated with the dis-.- charge device. 15 includes a pulse transformer l9 andlav pulse-forming. and pulseedetermining capacitivestorage element.26.. The capacitive element 2!! is preferablyv constituted by an open;-

ended artificial transmission .line section made up, of capacitors .2'! and inductances 22'... The anode I6 .is connected through aprimarywinding 23"of the transformer I9 tothe source of'unid'irectional' current supply indicated on the drawingby 13+. The open-ended, transmission line section; 29. is connected between the control electrcde I 8 and the grounded cathode I! in series circuiti'relation with aresistor 2.4 and a secondary .winding,25cf the .pulse transformer l9; The resiston'ld pr-eferablyha-s a resistance substantiallyzequal, to thesurge impedance. of the trans:-

The control electrode 18 is also connected tc.,the. cathode. [1 through asuitable grid bias resistor 26 and a. sourjce; or

winding pulse transformer 38.

negative bias potential, such as a battery 21. The pulse output from the discharge device I5 is supplied from a tertiary winding 28 on the pulse transformer l9.

In operation, the pulse generating circuit including the discharge device l5 functions in the following manner. When a triggering impulse renders the discharge device I! conductive, current from the positive potential source B+ through the primary winding 23 of the pulse transformer l9 to the anode of the discharge device l I induces at the ungrounded end of the secondary winding 25 of the pulse transformer 19 a positive potential, thereby driving the control electrode l8 of the discharge device l5 positive and impressing across the input end of the transmission line 20 a short voltage pulse. The discharge device l5 thereupon begins to conduct.

The additional current through the transformer winding 23 resulting from conduction of the de: vice l5 induces an additional positive potential in the winding 25, so that the control electrode I3 is driven more positive and the discharge device 15 driven rapidly to saturation. Conduction continues until the voltage pulse impressed across the input end of the transmission line 20 travels to the remote open end and reflects back to the input end. This reflected pulse is of such polarity and intensity that it drives the control electrode ll} of the discharge device abruptly negative and beyond cut-off, thereby suddenly terminating conduction in the device 15. Thus, the period of the pulses derived from the output of the discharge device !5 is determined by the reflection characteristics of the transmission line section 29, and the frequency of the pulses is determined by the frequency of the triggering impulses received from the discharge device II. It will, of course, be understood that the maximum permissible triggering-frequency is limited by the time necessary for the transmission line 20 to discharge through the resistor 26.

, A regenerative pulse generating circuit of the type described immediately above is described and claimed in the copending application of Harold W. Lord, Serial No. 464,033, filed October 31, 1942, now United States Patent 2,444,782, is-

sued July 6, 1948, and assi ned to the same assignee as the instant application.

The voltage pulses derived from the output winding 28 of the pulse transformer I!) are supplied to the input circuit of an amplifying electron discharge device 39 having an anode 3!. a grounded cathode 32, and a control electrode 33.

The pulse transformer winding 28 is connected between the cathode 32 and control electrode 33 in series circuit relation with a suitable source of negative bias potential, such as a battery 34 and a grid bias resistor 35 shunted by a capacitor 36.

The anode 3! of the amplifying discharge device 30, is connected to the positive potential source 3+ through a primary winding 31 of a three- Positive pulses appearing at the upper terminal of the pulse transformer winding 28 in response to recurrent pulsed conduction of the discharge device I5 re currently render positive the control electrode 33 of the discharge device 30 thereby to produce amplified negative voltage pulses upon the anode 3| of the device 30. These amplified pulses appear across the primary winding 31 of the pulse transformer 38 and induce pulses of opposite polarity in a pair of oppositely wound secondary windings 39 and 40 on transformer 38.

The pulse transformer winding 39 is grounded at one end and connected at its other end to supply positive pulses through a coupling capacitor 41 to a control electrode or grid 42 of the cathode ray discharge device I. The discharge device I comprises an evacuated discharge envelope 43 having at one end a grounded cathode 44 and at the other end an anode 45. A suitable source of unidirectional current supply, such as a battery 46, is connected between the cathode 44 and anode 45, and the cathode ray discharge is controlled by the grid or control electrode 42. The grid :52 is provided with a negative bias from a source 42a through a resistor 42b. When the electrode 42 is sufficiently positive to permit the projection of an electron beam from the cathode 44 through the anode 45, the beam passes between two pairs of deflecting plates 41 and 48 and falls upon a sensitive screen 49 of a suitable fluorescent material. The deflecting plates 48 and 49 are preferably arranged to deflect the beam laterally along mutually perpendicular axes.

The pulse transformer winding 41! on the pulse transformer 38 is connected at one end to the positive potential source B+ and at the other end through a unilateral conducting device, such as a diode rectifier 55!, to the anode am of an electron discharge 5i, and is so disposed that voltage pulses induced. in the winding in response to voltage pulses in the wind ng 31 oppose the voltage of the source 15+. The intensity of the voltage pulses in the winding is is substantially equal to or greater than the intensity of the voltage of the source 78+. The electron discharge device 5! is preferably of the pentode type and includes, in addition to the anode 5la, a cathode 52, a control electrode or grid 53, a screen grid 54, and a suppressor gr d 55. The cathode 52 is grounded and the control electrode 53 and suppressor grid 55 are connected together and to the cathode. The screen grid 5c is connected through a bias resistor 56 to the source of unidirectional potential 13+ and through a condenser 51 to ground. The positive bias impressed upon the screen grid through the resistor 56 is sufficient to render the discharge device 52 normally conductive. Furthermore, it is well known that the arrangement of the remaining grids in a pentode discharge device of this character is such that the magnitude of anode current remains substantially constant over a wide range of anode potentials.

A plurality of capacitors 58, 59, and Ell are arranged to be selectively connected between the anode 5! a and cathode 52 of the discharge device 5| by means of a selector switch 6|. As shown on the drawing, the low capacitance point 62 of the selector switch Si is an open circuit. In this connection, the only capacitance between the anode and cathode is that introduced in the circuit by the interelectrode capacity itself and the capacitance of the various leads and selector switch parts.

The circuit including the discharge device 51, the diode rectifier 5i and the capacitors 58, 59, and generates a saw-tooth voltage wave utilized to effect a recurrent timing sweep of the cathode ray beam along one axis of the fluorescent screen ts. For this purpose, the anode 5| a of the discharge device 5! is connected to one of the horizontal deflection plates 48 in the cathode ray tube 43. The other plate 48 is grounded, so that the voltage between the plates 48 is that between the anode a and cathode'52 of the discharge device 5!, as determined by the selected condenser 58, 59, or 60.

' :Ehe -sweep :circuit described :above. operates {in allowing, manner @to. produce'sawi-toothioscila lations. Whenmmpulse -voltageiispresentiin the primary windings"? offitherpulsertransformer 38, no --voltage "is induced in the tertiary winding .49. ilhus,:norma1ly the diode rectifier 50 :is conductive and current flows from 13+ rthrough-thetertianyiwi-nding A0, zthe diode rectifier:- 519, and :the positively biased pento'deldisch-arge device "15' *to ground. During conduction or the discharge device 5 11 from :the source 'Br l thecselected-condenser 58,"-59 or ii remains chargedto; a constant --voltage :equal to the :voltage/droybetween the anode -51 a-and cathode 52 :of :the :discharge des vice" -"Whenever a voltage pulseappearsiin thertrans- "formerwin'd-ing 3l,--a pulse ofsvol-tage isiinducedsin the transformer winding 49 itt-Swill 5a direction :as= to mppose "the voltage :of the unidirectiQIlfil 'voltage source 33+. "Since :the pulse voltagezz'is equal to or greater than the unidirectional volt! tage, the net voltage aroundrthei circuit? including the diode "rectifier 55a and rpentodesdischargerde- .vi'ce 5! is reduced :to zero or-rreversed, so. thatsthe diode rectifier'fill becomesznomcontluctive and-rel- --mains:non-conductive foritheperiod :ofatherpulse. "During this pulse period, thezselected rcharged capacitor 58; 59, or 68.1serveslas avparallel voltage Source and continues the discharge throughatl re discharge s'deviee. 251 :fDischa-rge :of the capacitor :throughzthezsourceiBel-.zisrprevented'j-by theidiode #59. ZAsithe energyrstored iin the sweep capacitor :5859,ror fiflsdiminishes,rthervoltagezofvthe capacitor 'decreases. 7However,:as previously -;pointed out, :the-:current through the; discharge device: 51 remains :constant lover-a wide range of .--a-node .voltagea sothat the sweep capacitor isdischarged art/substantially constant :current. As is well .lknownfito thoseskilled instheart; a. constant curvrcn t discharge of :a capacitor efiects-.:a-:s,ubstantially iinear decreasedn capacitorwoltage. 'jItiis :the linearly :decreasing sweep -.-capacitor uvoltage 'whichfisnpplie'di between the horizontal. deflection plates of: thecathodevray discharge: device :;4;3.

-As=soonas thevoltage pulseinzthe pulsettrans -former winding 49 is terminated the diode recti- =Tfierfi 50 -again becomes: con'ductive.-wa-nd :the source 513+ supplies current to the *discharge deviceiil- *When the rectifier '5fltbecomesconductive ."at the term inationof -a pulsa the voltage 10f the anode 5 lwof the discharge device- I is :raised suddenly, therebymbruptlwto increase the charge and the voltage-of: the sweep-capacitor 5B, 59, or 50. Thus, the cathode ray beamis moved along the horizontal axis ofithefluorescent-screen 49 at a substantially. constant rate-determined .by the rate of voltage diminution of the sweep ,eapacitor: during discharge .,to .-.establish,a time base for wave analysis and is suddenly returned to its starting ,point, when the sweep capacitor voltage is -abruptly'increased- -upon-termination ofthe pulse voltage in the winding 49.

The sweep circuit comprising devices 50 and 5| and capacitors 58 59, 69 is particularly claimed in our copending application, Serial No. 663,319, filed April 19, 1946, now United States Patent 2,457,522, issued December 28, 1948, which is also a division or the aioresaid application, Serial No. 563,920 new United States Patent 2,449,801, issued September 21, 1948.

The positive pulses appearing. on the pulse transformer secondary winding 39 are supplied not only through the coupling ndenser 4| to the control grid 42, but also through a lead 63 to a time'delay or phase Shifting circuit 64 to contr01-..a trigger pulsegenerator'jfi. yPulses inf-1211c transformer winding :39 are coincident in with vthose in-.the-;transformer winding 40 wt: chcontrolthe: discharge :of .thesweem capacitors Q9. 5'9, andifi0. 1 Pulses iromgthezpulse generatcriidfl layed -;in time with respect to pulses in the mindings F39 and 4,0zare amplified -in-:a ,discharg vice 16.6 Land supplied nth-rough a transformer j to :trigger :or render operative the sourc 2 mi oscillations :tozbe observed or analyzed. cillations to be analyzed' irom the .source :1- su-pplied i the vertical deflection plate df'lifl he cathodeiraydischarge. devicey li3. 'Thus thegsingie pulse itransformer fiil serves twin-itiate to simultaneously establish a cathode gray throughicontrol ofzthegridor intensifier 542 Y nd torrender operative'the sourced! orobserve cillations through the "time delay.circuit ,6.4 trigger :puI-se generator 65. ithc zlilf fi pulses are synchronizedwithsand delayedriri ape withcrespectstoythe: initiation of the %beam.1:-sweep.

The time :delay. circuit 64 comprisesgapsourcergf substantially -.constant unidirectional potential, suchassa batterysfi8,..connected:in 011130511191 sends circuit :relation with 'gthe pulse: transformer see: ondary winding 13-9 .acrossan integrating-16' it consisting of a :variable resistor ;=69 land capacitpr 1:9. A primaryzyvinding 1|. Dfzfi pulsetransformer 1 2 :isconnected:acrossthe. condenser" 1:0 athroughia unilateral conducting device such; asa. diofdcre i. tier- 1 3. =This circuit functions .1110 zestablishsi th transformer winding J: I 1 a recurrent series oil-volt- -age=pulses delayed intime or :phaseyrelatiomwith respect to the series of recurrent voltage pulses appearing :in the transformer winding 39.

t'l heoperationl of the time delay circuitzififl ide- =pends-npon =':the. characteristics ofthe integrating circuit 69,118. iwhenzno voltage pulse is/prcsent in vthe transformer winding :39 :wthe battery 2.6) maintains the condenser :10 charged to at-he *hatr tery voltage. 'Whenever a pulse :appears upon the transformer winding: 39, the pulselvoltage-rope poses the Ivoltagev of =thevbattery :68. Sinceazthe pulse is of:- substantially' rectangular wave .zshape I :and its in'tensity ais l greater than the ivoltagezlpf :therbattery -68,;.the: sudden reversal of- :voltage -'-plied' to the-con'denser'i'lfl causes the acondensicr charge to decay exponentially .to zeroeand {then *tomeverse. --As soon--as:the voltage-Mathe son? denser illreverses, 'the'voltagenapplied torthe unilatera'lly :con'ducting circuit through the-vpulse transformer winding H is reversed, so ithat pthe diode rectifier 'l3 becomes. conductive etc: applyaa -triggering pulse to Jthe: transformer-rwin'di-n .l, It -Will thus he-evident that the time :delay,;b.etween the -initiationof apulsein the transformer --winding '39 and 1 the i-ini-tiation ,1 of 1a pulse in the :transrormer-windingi! I is determined bwthe; me --taken for the charge of the condenser 'llrtoz'decay :exponentially ---to :zero and :to reverse suf-ficiently ato wonder :the discharge-116mm '13 :conductive. This time is determined by the resistancecfthe resistor 69 and the capacitance of the capacitor '50, and may suitably be controlled by utilizing a variable resistor 69, as indicated on the drawing. Upon termination of each pulse in the transformer winding 39, the battery 68 again reverses the charge upon the condenser 10 and brings it back to its normal value. The triggering pulse in the transformer winding H is not necessarily of the same duration as the initiating pulse in the transformer winding 39, but its duration is determined by the length of time for which the volt,- age of the capacitor (0 remains reversed by the voltage pulse in the transformer winding 39.

transmitter operative.

The pulse generating circuit 65 is similar to that previously described comprising the artificial transmission line and the electron discharge device l5. The pulse generating circuit 65 comprises an electron discharge device 14, an artificial transmission line 15, a source of negative bias potential such as a battery 16, a grid bias resistor 11, a resistor 1'8 between the transmission line 15 and the control electrode of the electron discharge device 74, and the pulse transformer 12. The operation of the pulse generating circuit 65 is entirely similar to that of the pulse generating circuit previously described, the only difference beingthat in the circuit 65 the triggering pulses are supplied through the transformer winding H rather than directly to the anode of the discharge device 14. An output winding 19 of the pulse transformer 12 supplies to the input circuit of the amplifying discharge device 66 a series of recurrent voltage pulses having a length or period determined by the characteristics of the transmission line 15 and a frequency determined by the frequency of the delayed triggering pulses derived from the pulse transformer 38. The amplifier BB is similar to the amplifier 3B and its input circuit comprises a source of negative bias potential such as a battery 80, a grid bias resistor 8|, and a shunting capacitor 82. The amplified trigger pulses from the transformer 61 are supplied to the oscillation source 2 to render the source 2 operative in synchronism with the beam sweep. The oscillation source or generator 2 is connected to the vertical deflection plates 4'! of the cathode ray discharge device 43.

By way of illustration of one application of our invention we have illustrated upon the fluorescent screen 49 a typical picture which may appear in the event that the oscillation source 2 is a radio direction and range finding apparatus of the type comprising a pulse transmitter and a receiver of echo or reflected pulses. In accordance with our invention, the cathode ray beam is turned on and horizontal sweep of the beam initiated at the beginning of each pulse appearing upon the transformer winding 31. The horizontal sweep of the beam traces a line 82 upon the fluorescent screen 49. synchronously with the initiation of the beam sweep and in fixed time delay relation with respect thereto, triggering pulses are supplied to the source 2 through the circuit 64 to render the Upon triggering of the transmitter, a transmitted pulse 83 appears upon the fluorescent screen 49 by operation of the source 2 and the vertical deflection plate 41. In the event that the pulse 83 encounters a detected object and is reflected back to the receiver of the source 2, a reflected pulse 84 will appear upon the fluorescent screen 49 a predetermined time after the pulse 83, as determined by the distance between the source 2 and the reflecting object. In this manner, the range of a reflecting object may be determined.

While we have shown and described only a preferred embodiment of our invention, many modifications will occur to those skilled in the art and we therefore wish to have it understood that we intend in the appended claims to cover all such modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure Letters Patent of the United States is: p

1. A time delay circuit comprising a source of recurrent voltage pulses and a substantially con stant voltage source connected in opposing series circuit relation, said voltage pulses exceeding said constant voltage in magnitude and each havinga predetermined duration, an integrating circuit in,- cluding a resistor and a capacitor connected in series circuit relation across said voltage sources, a load circuit, and a two-electrode rectifying device connected in series circuit relation with said load circuit across said capacitor, said capacitor being charged in one direction from said constant voltage source in the intervals between pulses and then discharged and recharged in the opposite direction during each of said pulses, said device being poled to be normally maintained nonconductive by said voltage source and to conduct only when said capacitor charge reverses, thereby to provide a delayed current pulse through said load circuit.

2. A time delay circuit comprising a source of recurrent voltage pulses and a substantially constant voltage source connected in opposing series circuit relation, said voltage pulses exceeding said constant voltage in magnitude and each having a predetermined duration, an integrating circuit including a resistor and a capacitor connected in series circuit relation across said voltage sources, a load circuit, a twoelectrode rectifying device connected in series circuit relation with said load circuit across said capacitor, said capacitor being charged in one direction from said constant voltage source in the intervals between pulses and then discharged and recharged in the opposite direction during each of said pulses, said device being poled to be normally maintained non-conductive by said voltage source and to conduct only when said capacitor charge reverses, thereby to provide a delayed current pulse through said load circuit, and means to vary the value of said resistor to vary the time required for said gapacitor to discharge and recharge during said pulses.

FRANK J. BIAS. HAROLD W. LORD.

REFERENCES CITED UNITED STATES PATENTS Name Date Zepler June 30, 1942 Number 

